SOLUTION: I stand on a building 640 feet high and throw a rock into the air with a velocity of 96 ft/sec. When does the rock have a height of 800 feet?
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Question 762367: I stand on a building 640 feet high and throw a rock into the air with a velocity of 96 ft/sec. When does the rock have a height of 800 feet? Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! I stand on a building 640 feet high and throw a rock into the air with a velocity of 96 ft/sec. When does the rock have a height of 800 feet?
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h(t) = -16t^2 + 96t + 640
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Solve:
-16t^2 + 96t + 640 = 800
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-16t^2 + 96t - 160 = 0
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-16(t^2 - 6t + 10) = 0
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Quadratic formula:
t = [6 +- sqrt(36-4*10)]/(2)
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Since 36-4*10 is negative there is no Real Number solution.
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The rock never teaches a height of 800 ft.
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Cheers,
Stan H.
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